Power drive mechanism and control means therefor



POWER DRIVE MECHANISM AND CONTROL mus THEREFOR Filed Dec. 5, 1950 P. E. SHERRILL, JR

Aug. 5, 1952 6 Sheets-Sheet 1 INVENTOR UUU'Q-ILJ BY. ail/2&5

I ATTORNEYS.

POWER DRIVE MECHANISM AND CONTROL MEANS THEREFOR Filed Dec. 5, 1950 Aug. 5, 1952 P. E. SHERRILL, JR

6 Sheets-Sheet 2 w w w INVENTOR: Price liSfierrilLe/f. BY @144 3 6 A TTORNEYS.

Aug. 5, 1952 P. E. SHERRILL, JR

POWER DRIVE MECHANISM AND CONTROL MEANS THEREFOR Filed Dec. 5, 1950 6 Sheets-Sheet 3 STOP INVENTOR: 'Priqe E. Sfierrl'll, Jr. BY 632 44651 ATTORNEYS.

Aug. 5', 1952 P. E. SHERRILL, JR

POWER DRIVE MECHANISM AND CONTROL MEANS THEREFOR Filed Dec, 5, 1950 6 Sheets-Sheet 4 ATTORNEYS.

INVENTOR:

g- 1952 P. E. SHERRILL, JR 2,606,265

POWER DRIVE MECHANISM AND CONTROL MEANS THEREFOR Filed Dec. 5, 1950 6 Sheets-Sheet 5 STOP 7,3 Ji'lfifi- 39 SLOW INVENTOR: P170 EZS/zerrii I J1:

ATTORNEYS.

g- ,1 P. E. SHERRILL, JR 6 POWER DRIVE MECHANISM AND CONTROL MEANS THEREFOR Filed Dec. 5, 1950 6 Sheets-Sheet 6 12 3&1

INVENTOR: Pricg E SfiEf/ZZZ, J7:

ATTORNEYS.

be of the induction type.

Patented Aug. 5, 1952 UNITED STATES PATENT OFFICE POWER DRIVE MECHANISM AND CONTROL MEANS THEREFOR Application December 5, 1950, Serial No. 199,342

Claims.

This invention relates to power drive mechanisms and control means therefor.

In the operation of various kinds of textile machinery such as slashers and beamers, accurate speed control is essential for the maintenance of even tension on the yarns to insure uniform Winding upon the beams. At the present time, alternating current is the only form of electric power available in most localities, and, by reason of the difficulty of controlling them, motors powered from this source are not suitable as a means for driving such machinery with smooth gradation between very slow and high speed limits.

The principal objective of my invention is to provide means for overcoming the above mentioned difficulties. This objective is attained, as more fully disclosed hereinafter, through the use of a shunt field D. C. motor as the prime mover in conjunction with a D. C. shunt field generator driven by an A. C. motor which may The D. C. generator supplies the current for operating the D. C. motor, and variable resistance control means for regulating the speed of the D. C. motor are connected in circuit with the fields of the D. C. generator and the D. C. motor. A reversible A. C. servomotor for actuating the variable control means is utilized; and also a control system for electrically connecting the D. C. motor to the generator for starting at a definite slow or creeping speed. Means are included for starting the servomotor to actuate the variable control means and to thereby gradually reduce the resistance in the field circuit of the D. C. generator and add resistance in the field circuit of the D. C. motor in order to accelerate the latter to a definite high speed. In addition, automatic stop means are incorporated to stop the servomotor when the D. C. motor has attained a predetermined maximum speed. By manually controlled automatic means the servomotor is reversed to actuate the variable control means in the opposite direction thereby lowering the voltage of the field of the D. C. generator and decreasing the resistance in the field of the D. C. motor for return of the latter gradually to the slow or creeping speed; by other automatic means the servomotor is stopped when the last mentioned condition is reestablished. Automatic means is also operated to restore the system to its normal dormant condition.

In drive mechanism, characterized as above. it is a further aim of my invention to provide means whereby the stop means for the servomotor can be adjusted to predetermine the speed ranges of the D. C. motor.

Another object of my invention is to provide a preassembled control unit in which the variable control means is mechanically connected to the servomotor, and in which the stop means for said servomotor is arranged so as to be adjustable for the purpose above stated.

Other objects and attendant advantages will appear from the following detailed description of the attached drawings: wherein Fig. 1 is a diagrammatic view of my improved power drive mechanism.

Figs. 2-5 are similar views showing the control system under different conditions of operation.

Fig. 6 is a View, partly in top plan and partly in horizontal section, of a pre-assembled unit or device incorporating certain of the control instrumentalities employed in the system; and

Fig. '7 is a front elevation of the pre-assembled device with a portion thereof broken away to expose partswhich would otherwise be hidden.

With more detailed reference first to diagrammatic Fig. 1 of these illustrations, the numeral 5 designates the D. C. motor which is to serve as the prime mover and which is to be controlled, and 6 the D. C. generator which produces the current for operating said motor. The generator 6 is driven, through a mechanical connection 1, by a three phase A. C. induction motor 8 supplied with A. C. current from mains 9, l0 and Ill. The means provided for controlling the speed of motor 5 comprises a control unit or device (to be later more fully described), said device being represented by the dash and dot rectangle l2 and shown as including a pair of variable resistance control elements consisting of the potentiometer l3 and the rheostat I4. The contact arms 15 and iii of control elements [3 and I4 are both fixed upon a shaft l1 arranged to be rotated in one direction or the other, through a belt or sprocket chain is from the output shaft [9 of a reversible A. C. servomotor 20 of the capacitor start and capacitor run type. Also embodied in the device l2 are limit switches 2| and 22 which are arranged to be actuated by a contact finger 23 on shaft l1. Other instrumentalities utilized in the control of motor 5 include a transformer 25 with a primary coil 26 whereof one end is directly connected to the A. C. main II, and the other end connected, through a selector switch 21, to the main 0, and with two secondary coils 28 and 29; an electron tube 30 of the full wave rectifier type whereof the filament is connected across the terminals of the coil 28 and the plates or cathodes are connected across the coil 29 with interposition of resistors; relays 3!, 32, 33, 34; a reversing switch 35 for servomotor 20; and Start, Slow, Fast and Stop push buttons 36, 31, 38 and 39 respectively. These several instrumentalities are variously interposed in two different circuits of a wiring system, one an auxiliary 110 volt A. C. circuit of which the mains are designated 40 and 4|, and the other a D. C. circuit with mains 42 and 43 across which a pressure of 230 volts is maintained between the points A-B, by the tube 30 in cooperation with a resistance 44 and a choke coil 55 in a crosswise connecting conductor 46.

Operation Assuming the A. C. motor 8 to be running and drivin the D. C. generator 6, the system to be otherwise dormant as in Fig. l, the D. C. motor is set into motion at slow or creeping speed by pushing Start button 36 as in Fig. 2. As a result, the coil of relay 33 is connected across the mains in and 4| of the auxiliary 110 volt A. C. line, the current flowing through the coil of relay 33 from the main 40 by way of conductors 58, 55, the contact plate of closed slow limit switch 24, conductor 52, closed Start switch 36, and conductor 53 to the main 4!. By this actuation of relay 33, the coil of relay 32 is energized by current flow from the main 42 of the D. C. circuit by way of conductor 55, switch of relay 33, and conductors 56 and 57. With the relay 312 closed, D. (3. current will flow from main 52 through conductor fit, shunt field coil 6.! of D. C. generator 5, conductor 52, the effective resistance of potentiometer l3, conductor 63, switch plate 65 of relay 32, and conductor 86 to the main 63, and also from line 42 to said potentiometer by way of conductor 6 1a. At the same time, the armature of D. C. motor 5 will be connected across the armature of the generator 6 upon closing of a secondary circuit 66, 61, 68 by the bridge plate 69 of relaySZ. Upon release of Start button 36, the coil of relay 33 is kept energized by current flow in a lock-in circuit from main 60 through conductors 5!), it, the

bridge plate ii of relay 32, conductor 12, contact plate of Step button 39, and conductor 13 to main t i. Under these conditions, thegenerator 5 will deliver current for operation of the D. C. motor 5 at slow speed, the field coil M of the latter being energized by the D. C. current flow from the main 42 by way of conductors T5, T6, rheostat l4, and conductor l! to main #13.

If the Fast button 33 is now pressed as in Fig. 3, the coil of relay 31' will be energized by current iiow from main ii) by way of conductors 39, 8! and B2 to main ll. By actuation of the relay 3| another circuit is closed between mains ll! and s! through conductor 83, switch plate 85 of said relay, conductor 85, motor 20 and conductor 87. As a consequence, the motor 29 is driven in the direction of the arrow in Fig. 3 and the shaft i! turned in the same direction, with attendant retraction of the finger 23 from the slow limit switch 2i and gradual cutting out more and more of the resistance of the potentiometer i3 and adding resistance in rheostat Hi. The current flow in the field of the motor 5 is thus decreased and the current flow in the field of generator (5 is progressively increased and the rotation of said motor 5 correspondingly accelerated. It will be observed that during operation of the potentiometer l3 as just explained,

part of its resistance will be in series with the field of generator 6, and part thereof in parallel with said field. Upon release of Fast button 38, relay 3! is held temporarily closed by current how in a lock-in circuit from main 40 through conductors bridge plate 89 of said relay, conductor 9%, closed fast limit switch 22, conductor 3;, Slow switch 3?, conductors 82, 12, Stop switch 39, and conductor '13 to main 4i. When the motor 5 has attained full speed (the rate of which is predetermined as later on explained), the fast limit switch 22 is automatically opened by the finger 23, thereby breaking the circuit 80, 89, 9.9, 22, 9!, 3T, 92, i2, 39 and i3, with consequent opening of the relay 3! and breaking, in turn, of the circuit 85, ii! to stop the servomotor 26.

If, while the motor 5 is running at full speed, the Slow button 37 is pressed as in Fig. 4, the coil of relay 34 will be energized by current flow iron". main 4) through conductors 93, 94 to main 46. Upon closing of relay St, a circuit willbe established from main to. through plate 96 of relay 34, conductor 9?, reversing switch 35, conductor 9 3 and conductors Hi3, lfli and 87 to main M. The servomotor 2B is thereby reversed in rotation and kept running to operate the variable resistance elements I3 and [4, with attendant gradual decrease in the resistance in the field of the motor 5. and increase in the resistance in the field of the generator 6 until the finger 2.3 re-engages and opens the slow limit switch 2!. The motor 5 will thereupon operate at the predetermined low speed under the-conditions described in connection with Fig. 2.

If the Stop button 39 is pressed as in Fig. 5, while the motor 5 is running at full speed, the coil of relay 33 will be tie-energized by breaking of. circuit 39,59, 6, ii, 72, and followed by de-energization of the coil of relay 32 through breakingof circuit "32, 56, 5?, and opening of the latter relay. Here, however, the coil of relay 34 will be energized to bring about reverse rotation of the motor 26 for return thereby of the finger 23 to depress slow limit switch 2!. Upon such actuation of switch 21, the system will be restored to the dormant condition in which it is shown in Fig. l.

If the Stop button 39 is pushed with the motor '5 running slow as in 2, the coil of relay 33 will be d-e-energized by breaking of circuit 45, 51' it, "1!, E2, 73 and 46 as before, with consequent opening of said relay and restoration of the system likewise to the dormant condition of Fig. l.

The purpose of the tapped primary 26 of transformer 25 isv to secure the proper voltage on the electronic tube 35) in order to obtain the maximum output from the latter and thereby increase its longevity. If the voltage in the AC. line 6, i l is normal, the selector switch 2'! is set at the point 11. If it is high, said switch is set at the point e and if it is low, said switch is set at the point e as may be required.

In practice, the device diagrammatically represented at [2 in Fig. l is given the form illustrated in Figs. 6 and '7. As shown, it comprises a base I05 whereon is mounted the A. C. motor 20 together with a casing I65 in which the elements [3 and M are housed. Secured to the output shaft [9 of motor 2.0 is a leather faced clutch disk I87, and held in frictional engagement with said disk by a regulatable spring I08 is a sprocket wheel I09 which, through the chain it, is geared to a sprocket pinion ill! on the shaft l1 whereto the contact arms l and IE (not here shown) of the elements I3 and I 4 are afiixed. The finger 23, hereinbefore referred to, is made fast to the hub of the sprocket wheel I09 by a set screw III. The Slow limit switch 2! is secured to the back of a panel H2 upstanding from the front edge of the base I05, the same being so positioned that its actuating plunger H3 is in the path of the finger 23 as shown in Fig. 7. The Fast limit switch 22, on the other hand, is carried by a block H4 having a laterally projecting stud H5 which extends outward through an arcuate slot H6 in the panel H2 in concentric relation to the axis of the motor shaft I9. Free on the protruding end of the stud I I5 is a hollow clamp collar I I1 containing a loading spring I I8; and threadedly engaged with the stud is a hand wheel H9 which, when tightened, forces said collar against the panel H2 in opposition to spring resistance, to set the switch 22 in adjusted positions along the slot H6 in said panel, with its actuating plunger I20 positioned, like that of switch 2|, in the path of the finger 23. The ratio of the sprocket wheels I09, H0 is two to one, so that a half rotation of the motor shaft [9 will result in a complete rotation of the shaft IT. A stop block indicated at I2 I, serves, by cooperation with a stud I22 on sprocket H0, to prevent overtravel of the shaft I"! under drive of the motor 20, this action being allowed by slippage of the clutch disk I07 relative to the sprocket I09.

My invention is not necessarily limited to the precise details of construction and arrangement herein disclosed by way of example since, within the scope of the appended claims, these are subiect to considerable variation as will be readily understood by those skilled in the art of electric motor control.

Having thus described my invention, I claim:

1. A pre-assembled unit for use in an electric control system for power drives, said unit comprising a base; a reversible servomotor mounted on the base together with a rheostat having two co-axially arranged rotary variable resistance elements and individual contact arms afiixed to a common actuating shaft; gearing connecting the shaft of the motor with the contact arm actuating shaft of the rheostat; an upright panel rising from the base forwardly of the motor and rheostat; a pair of limit switches in spaced relation at the back of the panel; and a finger carried by the shaft of the motor and adapted to actuate one of the switches when the motor is 1 rotated in one direction, and to actuate the other switch when the motor is rotated in the opposite direction.

2. A pre-assembled electric control unit according to claim 1, wherein the limit switches are secured to the panel with capacity for relative adjustment along an arc having its center of curvature in the axis of the motor shaft.

3. A pre-assembled electric control unit according to claim 1, wherein the panel is provided with an arcuate slot having its center of curvature in the ax s of the motor shaft; and wherein at least one of the switches has a lateral stud projecting through the slot and a clamp wheel threadedly engaged on the protruding end of the stud, whereby the switch can be adjusted along said slot.

4. A pre-assembled electric control unit according to claim 1, wherein the finger is frictionally connected to the motor shaft for capacity to slip upon contacting either of the limit switches.

5. A pre-assembled electric control unit according to claim 1, wherein the gearing includes a sprocket wheel connected, through slip clutch.

means to the motor shaft and carrying the finger, a sprocket wheel affixed to the actuating shaft of the rheostat, and a chain connecting the two sprocket wheels.

PRICE E. SHERRILL, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 865,813 Powell Sept. 10, 1907 1,618,827 Jewitt Feb. 22, 1927 2,036,629 Grosvenor Apr. 7, 1936 2,070,590 Goldsmith Feb. 16, 1937 2,281,844 Jones May 5, 1942 2,303,499 Rich Dec. 1, 1942 2,433,130 Larsen Dec. 23, 1947 2,500,753 Higgs Mar. 14, 1950 2,512,745 Kebler June 27, 1950 

